The present invention relates to a tensioner for traction means, in particular belts.
Tensioners of this type are frequently used in belt drives of motor vehicles. For example, German Pat. No. DE 196 09 420 A1 discloses a tensioner having a housing which receives a cylinder for guiding a hydraulically dampened plunger in longitudinal direction. The interior space of the housing forms a reservoir for hydraulic oil, whereby hydraulic oil under pressure migrates out of the cylinder into the interior space, and whereby hydraulic oil is drawn from the interior space into the high pressure chamber of the cylinder. The interior space of the housing is closed by a cover which has a guide opening for passage of the plunger. The housing has a cylindrical receptacle for forming a seat for the cover, and a seal which is positioned outside of the cover, and thus is mounted in place following an installation of the cover. When mounting the seal, the distance between the cover and the seal becomes smaller, so that a gas cushion trapped between the cover and the seal is compressed. As a consequence of the thus-generated overpressure exerted by the gas cushion, the conventional tensioner suffers the drawback that the seal is pushed out of its seat again, and thus out of the cylindrical receptacle.